A new poll from a political action committee supporting U.S. Rep. Marsha Blackburn's bid for the U.S. Senate found her lead over former Gov. Phil Bredesen has narrowed in recent months.

The poll — commissioned by the Committee to Defend the President, which plans to spend heavily in an effort to help Blackburn — found 38 percent of those surveyed supported the Republican congressman while 35 percent favored Bredesen.

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A look at the several polls detailing the race of Marsha Blackburn and Phil Bredesen for U.S. Senate
Michael Schwab, The Tennessean

Eleven percent of respondents remained undecided.

The latest poll from the Committee to Defend the President is the third such survey the PAC has publicly released.

In both earlier polls, Blackburn had support of more than 40 percent of respondents — indicating that her support appears to have slipped in recent months.

Despite that, Amanda Head, a spokeswoman for the Committee to Defend the President, said "the future is still looking bright" for Blackburn.

"We will do whatever it takes to defend President Trump’s agenda from left-wing attacks and help Marsha as she prepares to support our president in the Senate.”

The Committee to Defend the President is a project of Stop Hillary PAC, a super PAC that started in 2013. Last year Stop Hillary PAC changed its name to the Committee to Defend the President, according to filings with the Federal Election Commission.

The PAC previously said it plans to spend $1 million on TV and digital ads and staff to help campaign for Blackburn.

Other polls from earlier this year have found the U.S. Senate race to be similarly tight, including a survey released last week from a Democrat-aligned PAC. That poll found Bredesen had a narrow lead over Blackburn.

The latest poll from the Committee to Defend the President, conducted over a three day period beginning July 9 by WPA intelligence , surveyed 551 likely Tennessee voters. It had a margin of error of plus or minus 4.2 percentage points.

Meanwhile, a new poll, released Monday, from Boston-based Emerson College found 43 percent of respondents supporter Bredesen compared to 37 percent siding with Blackburn.

The Emerson survey, conducted over a four day period beginning July 11 among 657 registered voters, had a margin of error of plus or minus 4.1 percentage points.

The poll also found 20 percent of Republicans said they would vote for Bredesen while 10 percent of Democrats would vote for Blackburn. Among independents, 44 percent of respondents favored Bredesen, compared to 27 percent for Blackburn.

Blackburn has yet to air television ads in the race while Bredesen has frequently run 30-spots on Tennessee airwaves since March.

More from The Tennessean

Both candidates face nominal opposition in the Aug. 2 primary. The two are expected to square off in a blockbuster matchup expected to draw national attention, given Republicans' narrow advantage in the U.S. Senate.

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Phil Bredesen and Marsha Blackburn are the leading candidates to replace Bob Corker in the U.S. Senate
Michael Schwab/USA TODAY NETWORK - Tennessee

Reach Joel Ebert at jebert@tennessean.com or 615-772-1681 and on Twitter @joelebert29.